A UC Davis study has identified a mechanism of attention in the human brain, previously identified in animals, that is responsible for shifts from distractible to attentive states. The study showed that administering the drug modafinil could alter the state of the locus ceruleus in the brain stem. After the drug was given, study volunteers shifted into a more attentive state in which they showed enhanced coordinated brain activity and performance on a test of attention control. The study also showed that the drug works by quieting activity in the locus ceruleus and increasing its connections with the frontal cortex, said Cameron Carter, professor of psychiatry and behavioral sciences and senior author of the study, which was published in the journal Science.